package com.cmy.dao;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

//操作数据库的公共类
public class BaseDao {
    private static String driver;
    private static String url;
    private static String username;
    private static String password;

    //静态代码块,在类加载的时候就初始化了
    static{
        Properties properties = new Properties();
        InputStream is = BaseDao.class.getClassLoader().getResourceAsStream("db.properties");

        try {
            properties.load(is);
        } catch (IOException e) {
            e.printStackTrace();
        }
        driver=properties.getProperty("driver");
        url=properties.getProperty("url");
        username=properties.getProperty("username");
        password=properties.getProperty("password");
    }
    //获取数据库的连接
    public static Connection getConnection(){
        Connection connection = null;
        try {
            //加载驱动
            Class.forName(driver);
            connection = DriverManager.getConnection(url,username,password);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return connection;
    }

    //编写查询公共类
    public static ResultSet execute(Connection connection,PreparedStatement preparedStatement,ResultSet resultSet,String sql,Object[] params) throws SQLException {
        //预编译
        preparedStatement = connection.prepareStatement(sql);
        //可能查多个对象,占位符从1开始,数组从0开始
        for (int i = 0; i < params.length; i++) {
            preparedStatement.setObject(i+1,params[i]);
        }
        resultSet = preparedStatement.executeQuery();
        return resultSet;
    }

    //编写增\删\改公共类
    public static int execute(Connection connection,PreparedStatement preparedStatement,String sql,Object[] params) throws SQLException {
        //预编译
        preparedStatement = connection.prepareStatement(sql);
        //可能查多个对象,占位符从1开始,数组从0开始
        for (int i = 0; i < params.length; i++) {
            preparedStatement.setObject(i+1,params[i]);
        }
        int updateRows = preparedStatement.executeUpdate();
        return updateRows;
    }

    //释放资源
    public static boolean release(Connection connection,PreparedStatement preparedStatement,ResultSet resultSet){
         boolean flag = true;
         if (resultSet!=null){
             try {
                 resultSet.close();
                 //GC回收
                 resultSet = null;
             } catch (SQLException throwables) {
                 throwables.printStackTrace();
                 flag = false;
             }
         }
        if (preparedStatement!=null){
            try {
                preparedStatement.close();
                //GC回收
                preparedStatement = null;
            } catch (SQLException throwables) {
                throwables.printStackTrace();
                flag = false;
            }
        }
        if (connection!=null){
            try {
                connection.close();
                //GC回收
                connection = null;
            } catch (SQLException throwables) {
                throwables.printStackTrace();
                flag = false;
            }
        }
        return flag;
    }
}

    